M. A. de Quatrefages on the Classification of the Annelides. 8 
those genera whose relationship was indisputable, and their affi- 
nities easily grasped. Now the class of Annelides, in conse- 
quence of its very great variability of type, presents a great num- 
ber of genera which, although composed of very well-known 
species, do not present this double character. In such cases I 
have not hesitated to isolate them—to place them, so to speak, 
outside the series—depending on the investigations of my succes- 
sors to assign them sooner or later a definitive place. Systematic 
minds, those who always require absolute conclusions, will pro- 
bably blame me for having acted thus ; but those naturalists who 
prefer certainty to rapidity of progress will, I hope, approve my 
course. I have also, of course, placed among the zncert@ sedis 
those species and genera upon which we are in want of sufficient 
data ; but I have endeavoured to determine at least the family 
to which they should be referred, and I believe I have succeeded in 
the great majority of cases. 
Another consequence of the precision which I have endea- 
voured to introduce in the establishment of the families has 
been that 1 have been led to increase their number more than 
had been done by any of my predecessors. Savigny only 
reckoned seven, which is due to the small number of species 
known in his day. Johnston increased this number to fifteen, 
Grube to nineteen, and Schmarda to twenty-one. Although I 
place Grube’s entire family Amitidea among the incerte sedis, I 
have thought it necessary to divide the class into twenty-six 
families. 
This multiplication of fundamental groups will not, however, 
at all surprise those who take account of the progress made 
since the publication of the ‘Systéme des Annélides’ (1820). 
Savigny only admitted twenty-six genera. Mulne-Edwards, in 
the second edition of Lamarck’s work (1880), admitted forty- 
nine. At the time of the publication of his ‘ Familien der Anne- 
liden’? (1851) Grube classified eighty-six genera. In 1861 
Schmarda, in his ‘ Neue wirbellose Thiere,’ admits ninety-seven. 
Now, by adding to the labours of my predecessors the results of 
my own investigations, either on the sea-shore or in the magni- 
ficent collections of the museum, I have arrived at the number 
of 245 genera, of which 181 have been able to be placed in a 
systematic series, and 64 still remain incerte sedis for reasons 
which I have just indicated. 
I do not, however, think that I have allowed myself to be 
betrayed into an exaggerated multiplication of these elementary 
groups. The number of constituent species has never appeared 
to me to be a real reason for effecting a breaking up which 
would not have reposed upon a totality of precise characters. 
This exigency has even led me to reject several genera established 
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